Monitoring system, method for the process-parallel monitoring of collision or overload situations in machine tools

ABSTRACT

In a monitoring system for the process-accompanying monitoring or detection of collision or overstress situations in machine tools ( 1 ), comprising a machine control ( 2 ) with one or more sensors ( 4 ) for detecting measured signals or measured signal curves, a monitoring means ( 6 ) in which a comparison of the measured signals or measured signal curves of at least one sensor ( 4 ) with stored monitoring thresholds is performed, and a bidirectional interface ( 8 ) between the monitoring means ( 6 ) and the machine control ( 2 ), it is provided that the monitoring means ( 6 ), apart from detecting collision or overstress situations in a machine tool ( 1 ) and transferring machine stop or machine reaction instructions to the machine control ( 2 ), also permanently stores the measured signals or measured signal curves of the sensors ( 4 ) as measured by the sensors ( 4 ) before, during and after a collision or overstress situation and the data and statuses of the machine control ( 2 ).

BACKGROUND OF THE INVENTION

The invention relates to a monitoring system for in-process monitoringof collision or overstress situations or conditions by means of eventdata recorders associated with machine tools.

Monitoring systems for the in-process monitoring of collision oroverstress situations at machine tools are capable of detecting machinecollisions in process and stopping the machine drives, mostly only thefeed drives, as fast as possible to avoid consequential damage.

Such in-process monitoring systems are conventionally provided with anelectric interface between the monitoring system and the machine controlto monitor, in-process, the signals of the sensors in monitoringsections predetermined by the machine control and to stop the machinevia the same interface if collision, overstress situations or toolbreakage, for example, is detected. So far, the interfaces between themachine tool control and the monitoring system have been substantiallyprovided in the form of parallel input and output signals for the SPCcontrol.

Such a parallel interface between the SPC and a tool and in-processmonitoring by a collision and overstress detection system exists, forexample, according to the BAPSI standard (Brankamp-Artis-Prometecstandard interface) which already allows for the transfer of data wordsas tool code or cutting code from the NC program to the monitoringsystem.

A known control of the Siemens Company comprises a so-called tachographwhich logs operational processes. The latter control system is notstarted by a measured or detected collision or overstress event, butsimply logs all operational processes, resulting in the disadvantagethat other reasons for machine damage caused by collision are notdetected.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a monitoring system forin-process monitoring of collision or overstress situations at machinetools which, in case of a collision or overstress situation, not onlyintervenes into the machine control but moreover permits a laterjudgment of the causes of such a collision and overstress situation.

According to the invention, an in-process monitoring system is providedfor the in-process monitoring or detection of collision or overstresssituations by means of a large permanent memory forming an event datarecorder, e.g., a flash disc, and preferably a field bus interfacebetween the machine control and the monitoring system, in connectionwith a data transfer between the electric interface of the machinecontrol and the monitoring system as well as in connection with a sensorsignal supplying collision-relevant measured signals.

The invention provides the documentation of collision or overstresssituations at machine tools by an event data recorder in order tosecurely detect the causes of such collision and overstress situationsshould they occur.

The invention is able to use the field bus interfaces (beside or insteadof the parallel interfaces) only recently offered by the controlmanufacturers, which permits a more extensive exchange of informationbetween the machine control that consists of the stored program control(SPC) or the NC control.

Such a system for documenting collision or overstress situations atmachine tools by an event data recorder in order to securely detect thecauses of such collision and overstress situations in the event theyoccur is presently unknown.

In case of a collision or overstress situation, it has not beenpossible, according to prior art, to later determine the causes thathave led to the situation. Since the economic damage by machineshut-down or machine damage may be considerable in these cases, thedetection of whether technical or human failure was the cause is ofconsiderable economic importance.

Furthermore, the determination of the cause of damage permits thedetection of defects in the machine components, or in the operationalprocess, or mistakes of operating persons and avoidance thereof in thefuture.

The monitoring system for the in-process monitoring and detection ofcollision or overstress situations among machine components or of toolswith machine components or workpieces or of workpieces with machinecomponents or tools in machine tools at least consists of

-   -   (a) one or more sensors for detecting measured signals or        measured signal curves as may be produced at collisions,        overstresses or damage to machine tools, which are to be equated        with at least one direction of force, a resultant force, a        pressure, a torque, a motor output, a motor current, even if it        is taken from the values of the motor current sensor of the        control, a vibration, an acceleration, a distance variation or a        structure-borne noise,    -   (b) a monitoring means consisting of monitoring hardware with        software, wherein a comparison of the measured signals or        measured signal curves of at least one sensor with stored        monitoring thresholds is made by monitoring and evaluating        strategies of a known and random type, such as static        thresholds, dynamic thresholds, thresholds of signal pattern        curves etc. in order to provide a corresponding report from the        monitoring system to the machine control to immediately stop the        machine tool or at least its feed drives, and    -   (c) a bidirectional interface between the monitoring hardware        and the machine control (consisting of the SPC and the NC        control), which effects a data exchange between the machine and        the monitoring system and is adapted, e.g., to activate the        monitoring system via a signal as soon as a feed slide moves and        even to transfer spindle-, tool- or even cutting specific        monitoring sections in the form of data words as different        numbers or instructions from the NC or SPC program to the        monitoring system for the purpose of dividing the monitoring        into different monitoring sections, and to transmit machine stop        or at least machine reaction instructions to the machine control        at the moment of detecting collisions or overstress situations.

Optionally, an operating means consisting of operating hardware withsoftware for operating and/or parameterizing the monitoring systemand/or for visualizing the measured signals may be provided.

Apart from detecting collision or overstress situations in a machinetool and transferring machine stop or machine reaction instructions tothe machine control, the monitoring system of the invention is alsocapable of permanently storing (a) the measured signal data records(measured signals or measured signal curves) of the sensors as measuredby the sensors before, during and after a collision or overstresssituation and (b) the data and statuses of the machine control that areof interest as to the detection of the causes of a collision oroverstress situation.

The measured signal data records of the sensors in the working memory orworking storage of the monitoring system are continuously logged. Onlyat the detection of the collision or overstress are the measured datatransferred into the permanent memory of the monitoring system.

The monitoring system continuously logs at least one measured signaldata record (measured signal or a measured signal curve) of each of thesensors into the working memory or working storage.

Preferably, the monitoring system continuously logs two measured signaldata records of each of the sensors into different working storagelocations with respectively different resolutions as to time, referredto as “long” and “short”. This means that one measured data record isstored in a small time window with high resolution and one measured datarecord is stored in a larger time window with lower resolution.

Upon detecting the collision or overstress situation, the measuredsignal data records are immediately transferred from the working memoryinto the permanent storage or permanent memory locations of themonitoring system and thus to the machine control together with thereport of this situation.

The measured data records (measured signals or measured signal curves)to be filed in the permanent memory location and having the “long”resolution as to time preferably start about 2 seconds before thecollision or overstress situation and end about 3 seconds thereafter.

The measured data records to be filed in the permanent memory locationand having the “short” resolution as to time preferably start about 100milliseconds before the collision or overstress situation and end about150 milliseconds thereafter.

Immediately with the report of a collision or overstress situation fromthe monitoring system to the machine control, the latter begins, bymeans of an appropriate software, to detect data and statuses of themachine control that are of interest as to the detection of the causesof a collision or overstress situation and to transfer them to themonitoring system via the interface between the machine control and themonitoring system in order to write into the permanent memory thereof,which serves as an event data recorder, by means of the software of themonitoring system.

Preferably, the interface between the machine control and the monitoringsystem is a field bus interface, such as, for example, a process datahighway or an interbus (as bidirectional interface).

At least one of the following data records and/or status parameters ofthe machine control is written into the permanent memory of themonitoring system with respect to the detection of the causes of acollision or overstress situation:

-   -   program name or number that has been active in the NC control,    -   record number where the NC program has been stopped by the        monitoring systems,    -   present tool number in the form of the T or p number,    -   operational mode of the machine (setting, jog, automatic),    -   programmed tool correction values from the tool correction        memory,    -   programmed zero point displacement,    -   setting of the override switch for feed,    -   setting of the override switch for spindle speed,    -   speed of the spindles,    -   programmed speed of the feed slides,    -   present speed of the feed slides,    -   programmed feed of the feed slides,    -   position or actual position values of the feed slides, and    -   date and time.

Immediately with the report of a collision or overstress situation fromthe monitoring system to the machine control, the monitoring system canwrite all states of the signals of the bidirectional interface betweenthe monitoring system and the machine control, such as those accordingto the BAPSI standard, into the permanent memory thereof.

Immediately with the report of a collision or overstress situation fromthe monitoring system to the machine control, all monitoring-relevantdata of the monitoring means, such as, for example, the position of themonitoring thresholds, the measuring ranges and gain degrees of thesensors, the characteristic values for filtering the measured signals,the monitoring mode, such as teach-in, setting etc., can be written inthe permanent memory thereof.

All the measured signal curves, signals, data and statuses to be storedin the permanent memory of the monitoring system with respect to adetected collision or overstress situation belong to an unmistakable andmarked data record.

All the measured signal curves, signals, data and statuses of a datarecord concerning a collision or overstress situation can be displayedand, if necessary, printed out by means of the operating means(operating hardware and software) for operating and/or parameterizingthe monitoring system and/or visualizing the measured signals.

BRIEF DESCRIPTION OF THE DRAWING

The single sheet of drawing is a block diagram of the monitoring systemof the present invention, and depicts the manner in which threshold andsensor-detected data are compared and utilized to generate an eventdetection signal which in conjunction with a bidirectional interface isutilized to control machine operation and through subsequent permanentstorage and like permanent storage of machine control data and statusescan be utilized to readily determine the basis for machine toolcollision and/or overstress condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The monitoring system for the in-process monitoring or detection of acollision or an overstress situation in a machine tool 1 with a machinecontrol 2 shown in the drawing comprises at least one or more sensors 4for detecting measured signal data records. The measured signal datarecords are supplied to a monitoring means 6 in which a comparison ofthe measured signal data records of at least one sensor 4 with storedmonitoring thresholds is performed for detecting collision or overstresssituations. In case of the measured signal data records violating themonitoring thresholds, the monitoring means 6 supplies a set ofinstructions to the machine control 2 in order to immediately stop themachine tool 1 or at least its feed drives 3.

The machine control is composed of a stored program control SPC for themachine tool 1 and a NC control for the drives 3. According to priorart, it is possible to bidirectionally exchange data and statusesbetween the stored program control SPC and the NC control.

Between the monitoring means 6 and the machine control 2, abidirectional interface 8 is provided, effecting a data exchange betweenthe machine tool 1 and the monitoring means 6.

The monitoring means 6 comprises a working memory 12 into which themonitoring means 6 continuously writes at least one measured signal datarecord of each of the sensors 4; in this connection, it is also possiblethat several measured signal data records of each of the sensors 4 arecontinuously written into different working memory locations of theworking memory 12 with a respectively different resolution in time.

Apart from detecting collision or overstress situations in a machinetool 1 and transferring machine stop or machine reaction instructions tothe machine control 2, the monitoring means 6 is also capable of storingthe measured signal data records of the sensors 4 as measured by thesensors before, during and after a collision or overstress situation aswell as the data and statuses of the machine control 2 in an event datarecorder 14 consisting of a permanent storage or permanent memory, e.g.,a flash disc.

Furthermore, the monitoring means 6 may be connected to an operatingmeans 10. All measured signal curves, signals, data and statuses of adata record concerning a collision or overstress situation can bedisplayed and, if necessary, documented by printout by the operatingmeans 10 for operating and/or parameterizing the monitoring systemand/or visualizing the measured signal data records.

Although a preferred embodiment of the invention has been specificallydescribed herein, it is to be understood that minor variations may bemade in the invention without departing from the spirit and scopethereof, as defined by the appended claims.

1. A monitoring system for in-process monitoring of machine tool eventscomprising: control means for controlling the operation of a machinetool and providing actual data and statuses of the control means, atleast one sensor means for currently monitoring at least one of machinetool collision events and machine tool overstress condition events andproviding current signal data, first means for storing said currentsignal data of the at least one sensor means for providing currentsignal data records of said at least one sensor means, second means forstoring threshold data for each sensor means, means for comparing thecurrent signal data of each sensor means and the respective thresholddata for each sensor means for determining at least one of machine toolcollision events and machine tool overstress condition events and uponexceeding at least one of the respective threshold signal datagenerating an event detection signal, bidirectional interface means foroperating the control means to immediately control machine tooloperation and to provide said actual data and statuses of the controlmeans in response to the event detection signal, and means responsive tothe event detection signal for permanently storing a data record of theevent, consisting of the current signal data records of the firststoring means immediately before, during and after the generation of theevent detection signal and said actual data and statuses of the controlmeans provided by said bidirectional interface whereby the cause of theat least one of the machine tool collision events and machine tooloverstress condition events is readily determined on the basis of thesaid data record of the event.